A CHEMICAL STUDY OF THE SPECIFIC ELEMENTS OF TUBERCULIN. I.

1. The specific precipitin reaction and the skin reaction given by old tuberculin are attributable to two separate substances present in this material. The cause of the reaction first mentioned is a non-protein gum which will be fully described in the following paper. The cause of the skin reaction is probably but not surely a protein. 2. Methods which have been suggested for the standardization of tuberculin by precipitin or complement fixation reactions should be revised.